What is "netcode"

Netcode is a blanket term for anything that somehow relates to networking in online games; netcode is a term most commonly used by gamers when discussing synchronization issues between clients and servers. The actual elements of a game engine that can cause so-called "netcode issues" include, among other things, latency, lag compensation or the lack thereof, simulation errors, and network issues between the client and server that are completely out of the game's hands. Netcode as a term tends to be used only in the gaming community, as it is not recognized as an actual computer science term.